Electronic-Specific Modeling of Nitric Oxide in a Recombining Air Plasma

An electronic-specific collisional-radiative (CR) model of Nitric Oxide (NO) is presented and applied to the study of a recombining air plasma. This plasma is produced at local thermodynamic equilibrium at 8000 K and 1 atm by a 50-kW Inductively Coupled Plasma torch and passes at high-velocity through a water-cooled tube that forces rapid cooling and recombination. The electronic-specific model takes into account NO(C 2 Π) predissociation, spontaneous emission from the C 2 Π and D 2 Σ + states towards the A 2 Σ + state, and quenching of the excited states by various colliders. This model, alongside two other electronic-specific CR models developed for NO at NASA, is compared to measurements of NO excited states and electron densities along the tube length. Better agreement is obtained with the model presented in this work, especially because of the NO(C 2 Π) predissociation and NO C 2 Π and D 2 Σ + spontaneaous emission toward NO(A 2 Σ + ). The electron overpopulation is also explained by the partial equilibrium between N and O atoms and electrons, and the slow depletion of N and O atoms by the NO recombination reactions.